Because the worldwide availability of sweet crude oil (i.e., low sulfur oil) is diminishing, the need to hydrodesulfurize sour crudes has increased the use of cobalt and molybdenum as catalysts for the removal of sulfur. Generally, alumina is used as a support or carrier for these catalysts. Coupled with the increased costs of disposal over the next decade, spent catalysts containing molybdenum and cobalt (which may also contain vanadium and nickel) provide a secondary source of metals.
A spent catalyst may contain, for instance, by weight 4% Mo, 8% V, 1% Co, 2% Ni, 10% oil, 10% coke, 10% sulfur and the balance alumina. The metal values in a spent catalyst may range by weight from about 2 to 10% Mo, 0 to about 12% V, about 0.5 to 4% Co, 0 to about 10% Ni, occluded oil, coke, sulfide sulfur, and the balance essentially alumina.
It would be desirable to provide an environmentally acceptable process for converting the sulfur and oil usually associated with the spent catalyst to CO.sub.2 and Na.sub.2 SO.sub.4, while recovering the metal values therefrom for recycle.